Cataract extraction is the most common ophthalmic surgical procedure perform in the United States. During cataract extraction, an incision is made at the edge of cornea followed by capsulorhexis and removal of the nucleus and lens material by aspiration and irrigation or phacoemulsification techniques. For a decade, replacement of the natural lens with an intraocular lens has allowed for improved postoperative vision. However, subsequent closure of the corneal incision by suturing results in surgically induced astigmatism, compromising the improved vision. The suturing procedure requires surgical skill and is time consuming. The surgically induced astigmatism is between one and eight diopters depending on the surgeon's skill, the size of the incisions and the type of suture used. Presently the amount of time required for suturing is between 15 minutes to 1 hour depending on the skill of the surgeon and technique. Surgically induced astigmatism is not limited to cataract surgery, it also occurs in corneal graft. It has been observed that the tightest sutures produce the greatest amount of astigmatism. The astigmatism requires correction by glasses or contact lenses, otherwise the patient cannot have perfect vision even with the best surgical techniques.
Previous methods of managing the surgically induced astigmatism have included selective suture removal, an adjustable running suture technique, external corrective lenses and addition of compressional sutures.
The amount and placement of an astigmatism can be observed with a keratoscope, an instrument for observing abnormal curvatures of the cornea. The most common form consists of a disc bearing black and white circles, which, in case of anomalous curvature, appear to be distorted figures instead of concentric circles. A more detailed discussion can be found in the American Encyclopedia and Dictionary of Ophthalmology. Of particular interest is a simple hand held keratoscope which can be used with a slit lamp or in the operating room with the microscope, in use since 1974, called a contact keratoscope. It is made of a clear inner cylinder and a white outer cylinder The white cylinder is engraved with eight lines so that when projected onto a small steel ball, the lines are equal in thickness and equally separated. The contact keratoscope is light in weight and does not noticeably deform the eye when placed on the sclera. It is presently used for surgical correction of high post-keratoplasty astigmatism and thermal wedge resection. A more detailed description and references can be found in Int. Ophthal. 4,3: 177-178, 1981. The keratoscope can be mounted for use with the slit lamp or microscope used during operation. The image projected by the keratoscope can be analyzed by computer. (Such a computer analysis is shown in Duane's Clinical Ophthalmology, 1990, vol 1., Chp. 64, pg. 7.) It is possible that other methods of measuring the surface topography of the eye could be used with the present invention.
Biological glue is a glue derived from fibrinogen, a protein found in the blood which is converted into fibrin during clotting. Fibrin is a white, insoluble fibrous protein which when mixed with thrombin acts as a glue. The fibrin and thrombin are available commercially or the fibrin may be extracted from the patients blood by means of plasmaphoresis (electrophoretic separation of blood components). The fibrinogen can be further concentrated by cryoprecipitation and/or lypholization Since the bond strength is a function of the amount of fibrinogen, a strength tailored to the incision can be made. Thrombin and fibrinogen having a moisture content of less than 3% are available through ICN Biomedicals. This glue has been used in nonsuturable hemorrhage, pancreatic injuries, craniofacial surgery, pluto-pulmonary fistula, nerve repairs, control of pulmonary air leaks, obstetrics and gynecology, heart ventricular ruptures, repair of giant scleral ruptures, dental surgery, plastic surgery, epikeratophakia, perforated corneal ulcers, frontobasal and orbital reconstruction following trauma without complications.
After cataract surgery, leakage from the sutured incision can occur. To prevent this a contact lens made from collagen is placed on the eye. Such collagen shields are absorbed by the body after one to three days.
Much of the time required for ophthalmic surgery is occupied with suturing. The time for this procedure can be reduced to 5 min. by the technique of the disclosed invention. Other surgical incisions resulting from ophthalmic surgery are conjuntiva-limbus incision during glaucoma surgery, and scleral-tennon-capsule incision during vitreous retinal surgery.
It is an object of this invention to provide a method of closing the corneal incision which will minimize postoperative astigmatism, minimize required surgical time and skill, and minimized postoperative complications and recovery times.